Switching-over device for electrical lighting installations for railway-trains and the like



H. GROB. SWITCHING-OVER DEVICE FOR ELECTRICAL LIGHTING INSTALLATIONS FORRAILWAY TRAINS AND THE LIKE.

APPLICATION FILED NOV- 9. I9I5.

1,348,171. PatenteaAug. 3,1920.

HUGO GROIB, OF ZURICH, SWITZERLAND.

SWITCHING-OVER DEVICE FOR ELECTRICAL LIGHTING INSTALLATIONS FORRAILWAY-TRAINS AND THE LIKE.

Specification of Letters Patent.

Patented Aug. 3, 1920.

Application filed November 9, 1915. Serial No. 60,507.

To all whom it may concern:

Be it known that I, H oo GROB, a citizen of the Republic of Switzerland,residing at Zurich, in the Canton of Zurich, Republic of Switzerland,have invented certain new and useful Improvements in Switching OverDevices for Electrical Lighting Installa: tions for Railway-Trains, andthe like; and I do hereby declare the following-to be a full, clear, andexact description of the invention, such as will enable others skilledin the art to which it appertains to make and use the same, referencebeing had to the accompanying drawings, and to letters of referencemarked thereon, which form a part of this specification.

This invention relates to electrical lighting installations for railwaytrains, and with regard to certain more specific features, to atrain-lighting system utilizing an axle-driven generator for lightingthe train and charging one or more storage batteries which serve tolight the train when the generator is at rest or is operating at too lowa speed to generate sufficient voltage for the purpose.

One of the objects of; the invention is to provide a simple andeflicient train-lighting system in which the parts are automaticallyeffective to accomplish their functions without the necessity for manualoperation.

In axlelighting systems for railway trains, it is ordinarily necessaryto switch over or change over the circuits as the train comes to rest.Usually the diminishing potential of the dynamo is utilized in some wayto effect this switching of the circuits. In such cases, when thepotential is regulated by purely electrical action, as is done ininstallations constructed according to U. S. Patent N 0. 994,510, and U.S. patent application, Serial No. 605,629, certain practicaldifficulties arise, and consequently it has been customary in effect thechanging over by means dependent upon the speed of the dynamo or train.But

the necessary mechanical connection with the revolving dynamo shaft hasrendered-it often impracticable to accommodate the switching apparatusin the interior of the vehicle for, the purpose of facilitating thecontrol thereof. Accordingly, a further object of the present invention1s to provide an improved switching-over effected by means suchinstallations to or .changingover device for electric lightinginstallations wherein the dynamo and storage battery are alternately andtemporarily in operation and wherein the changing over in theconnections between battery and generator is dependent on the variationin the strength of the exciting current of the generator. Obviously asystem employing means of this character permits of great freedom in theplacing of the switching-over apparatus. 7

Another object is to provide in trainlighting apparatus of the abovegeneral type certain details of construction whereby the above and otheradvantageous results are attained.

Other objects will be in part obvious and art pointed out hereinafter.

he invention accordingly comprises the features of construction,combinations of elements and arrangements of parts which are to beexemplified in the structure hereinafter described, and the scope of theap: plication of which will be indicated in the following claims.

The accompanying drawing shows one of various possible embodiments ofthis invention and is a diagrammatic general view of .the improvedapparatus used in connection with a train-lighting installation in whichthere is provided a dynamo A of ordinary construction, with twoindependent armature windings represented by commutator circles, 2, 3 ofwhich the larger one 2 gen crates, for example, thirty-two volts, andthe smaller one 3 about seven volts. At B is shown conventionally theexciting Windthe dynamo A. A battery is shown as comprising the twoequal halves C C which are interchanged at suitable' intervals, as aftereach stoppage of the train. The work circuit is illustrated at D. Theswitches F, G, whose armatures are preferably polarized, serve toeffect'the circuit changes to accompany the changes in generator speed,as will be pointed out hereinafter. The switch E limits the voltage uponthe work circuit, as hereinafter described.

At the initial conditions with the train at rest, switches F, G areinclined toward the right, whereby the two batteries C C are connectedin parallel to supply current to the work circuit D through the lowresistance coil H of the switch G. The coil 8 of switch E, responsive todynamo voltage, is of course deenergized, so that the blade 28 of saidswitch is in its lower position. The field winding B is likewisedeenergized.

As soon as the train starts, the residual magnetism in the dynamo Abuilds up in the windings associated with the low voltage commutator 3 avoltage which sends current by way of the lead 46, thence through theballast or constant current resistance R the blade 28 of switch E, inits lower position, lead 29, field winding B, and lead-39, thus enablingthe dynamo A to excite itself. Since the two commutators 2, 3 areconnected in series, the lead 46 is at a potential equivalent to the sumof the voltages across the two commutators; assuming the negative lead 7to be at zero volts potential, the normal pressure of thirty-two voltsacross the brushes of the commutator 2 would maintain the lead 39 atthirty-two volts, and the further normal pressure of seven volts acrossthe brushes of the commutator 3 would maintain the lead 46 atthirty-nine volts. As soon as the potential at the lead 46 becomeshigher than the potential at the blade 9 of the switch F, the coil Hthereof will change the direction of its current flow and will cause theswitch blade 9 to move toward the left and establish a chargingconnection between the dynamo lead 46, through the ballast chargingresistance R current coil H blade 9, to the battery (1. The chargingcurrent which enters the battery C as the dynamo volta e increases,flows through the current coil 1% and holds the switch G firmly in itsleft-hand or charging position. At this moment only the battery C isconnected to the external lighting circuit. a

The switch blade 27 is connected mechanically to the blade 9 of theswitch F. The blade 30 is likewise connected mechanically The blade 27when in its left-hand position, connects the dynamo lead 46 through thelamp resistance R blade 27, lead 31, and blade 30, to the load D inparallel with the battery C As the dynamo voltage increases, the load isassumed gradually by the dynamo, resulting in a corresponding decreasein the discharge current from the battery until finally the dynamobegins todeliver charging current into the battery C The to the blade-1Oof the switch Gr.

resulting reversal of current in the current coil H of the switch Gcauses the blades 10 and 30 of the switch to be shifted into theirleft-hand positions, whereby, first, the battery C is disconnected fromthe work circuit D and connected to the exciting winding B, and, second,the dynamo is made now to deliver the lighting current directly throughswitch blade 30, instead of through lead 46 and lamp resistance R Bythis connection of the battery C to the exciting winding B, the dynamo Ais converted from a self-exciting erator into a dynamo of constantvoltage, the voltage of which is regulated on the principle embodied inmy U. S. patent application, Serial No. 605,629. The regulation isaccomplished by the use of the ballast or constant current resistance Rwhich is in series with the field winding B across the leads 46 and 39,the battery C being connected to the junction between this resistanceand field, with the other terminal of the battery connected to the lead,7. The ballast resistance R permits a limited predetermined quantity ofcurrent to pass through it, and this current divides between fieldwinding and battery. At a predetermined dynamo speed, the bat tery maybe assumed to be floating. If now, the dynamo speed increases, thedynamo voltage tends to increase, and the battery takes an increasingamount of charging current. Since, however, the sum of the current tobattery and field is constant (limited by the resistance R the fieldcurrent is reduced, thus reducing the dynamo voltage to its former andconstant value. The dynamo voltage thus adjusts itself at every speed tosuch a degree that the regulating battery C will take away from theconstant current passing through the ballast resistance R just such anamount that the remaining current flowing through the exciting coil B isjust sufficient to produce the proper dynamo voltage. It will be readilyunderstood that even at an excessively high speed of the dynamo, itsvoltage (disregarding residual magnetism) cannot rise high enough tocause the regulating battery C to take the entire current which isallowed to pass through by the resistance B since then the excitingcurrent would have become equal to zero in the field circuit B.

In consequence of the smallness of the charging current which flows intothe battery C the counter electro-motive force of the battery willremain for a certain space of time in the neighborhood of about 2 to 2.2volts per cell according to its condition of charge. The voltage acrossthe brushes of the large commutator remains, practically uninfluenced bythe speed of the dythe uppermost lead and shunt gennamo, within theselimits, but is reduced by the voltage drop of about one volt in terminalis connected to the the exciting winding B; this also applies to thelighting voltage. Then owing .to the addition of the voltage of thesmall commutator, the battery C also receives an approximately constantof suitable intensity. The low ballast resistance R is inserted'in thecharging lead for the purpose of settingan upper limit to the chargingcurrent.

Although the quantity of current flowing into the regulating battery Cis small, the counter electromotive force of this battery and thereforethe voltage of the work circuit would in time assume a high value. Inorder to avoid this, thereis inserted in the lead 31 the blade 28 of aswitch E which comes into operation as soon as the voltage in the workcircuit has attained a predetermined maximum value. Then the currentsupply through the resistance R to the exciting winding B ceases, andthe dynamo voltage drops until the battery C is delivering current,through the current coil H, blade 10, lead 6 and field winding B,thereby replacing the former arrangement of obtaining the field currentfrom the dynamo lead 46 through the ballast resistance R The regulationof the voltage is now effected in accordance with my U. S. Patent No.994,510. The negative terminal of the field winding B is connected tothe lead 39 as before, and the positive terminal 6 of the field isconnected, as-before, to the positive terminal of the battery C whosenegative dynamo return lead.7. At the minimum operative dynamo speed,the battery may be assumed to be supplying a maximum current to thefield.

If now, the dynamo speed increases, the

voltage across the leads 39-7 tends to increase; and since the voltageacross the field isequal to the (constant) battery voltage minus thevoltage 39-7, it is obvious that this increase in the voltage 39-7reducesthe voltage across the field, thus reducing the field current andthereby reducing the dynamo voltage to its former andconstant level. Inthis manner the dynamo voltage at every speed is automatically adjustedto a value so much less than the voltage of the battery C that a voltagediiference is produ'ced at the terminals of the exciting winding B,which difference is just sufiicient to cause that amount of excitingcurrent in the winding B which is necessary for enerating the properdynamo voltage. ince as hereinbcfore stated, thepotential across thefield B for full generator load at minimum operative generator speedneed not exceed one volt, the dynamo voltage across the leads 397 neednever be more than one volt lower than the voltage across the battery Ceven at the lowest operative speed of the charging voltage functionalvalue of connection between this latter circuit and v the dynamo isbroken.

7 In order to do this automatically,

the present invention provides for, the control of the disconnectingdevices by the change in the value of the exciting current flowing inthe winding B. For this purpose, the operation of the switch G is madeto take place responsively to a the exciting current. The excitingcurrent is led directly through a current coil H associated with theswitch 'G so that the action of the latter is dependent upon theregulating current flowing through the battery C. This current flowsinto the regulating battery C as long as the armature of the switch E isnot attracted; when the coil 8 of the switch E is energized, theregulating battery C then begins to discharge; as explained above.

' Hence the switch G is operated under either of two conditions; First,with switch E not fully energized and the blade 28 in its lowerposition, the field current is equal to the difference between thecurrent through resistance R and the automatically varying chargingcurrent to battery C if the dynamo speed is sufficiently high, or, as inthe present case, when the dynamo speed is assumed to be nearing itslower operative limit, the field current is equal to the current throughthis resistance R plus the automatically varying discharge current fromsaid battery C Assuming for example ten amperes as the maximmnpermissible field current, and eight amperes as the current constantlydelivered through the ballast resistance R then the witch G shouldoperate as soon as the battery current reaches two amperes. Second, withswitch E enercharging current from the battery C so thatthe switch Gshould operate when the battery current attains ten amperes. Thisoperation of the switch G at two or ten amperes is effected by providinga voltage coil H on the switch G, to be traversed by current only whenthe switch E is energized. This winding H adds as many negative ampereturns as are necessary to counteract the action of eight amperes in thecurrent coil H If the switch G is operated when the switch E is notsufficiently energized, the dynamo becomes an ordinary shunt dynamo,

, diately afterward.

whose potential drops with diminishing speed. After sullicient drop inthe dynamo voltage a reverse current flows from the battery to thedynamo. and the switch F is thrown to the right by the reversed currentin the coil H the battery C being thus connected again to the workcircuit 1).

()n the other hand, if the switch G is operated when the switch E isenergized, the dynamo is suddenly deprived of its excitation, andtherefore its voltage fallsvery quickly. The switch I is operated imme-In such a case the battery which has been on charge, is connectedsuddenly to the work circuit D, and an upward flickering of the lightswould occur. In order to avoid this, the switch (i may be combined witha device which will interrupt the circuit of the coil 8 of switch Emomentarily at every reversal of the switch G. This interrupting deviceis represented diagrammatically in the drawing by the pairs of contacts2-l and 26, and the insulated short circuiting piece 25. If the switch Gchanges its position while the coil 8 is energized. the latter willrelease its armature 2S, and thereby connect the dynamo field to thedynamo lead 46 for selfexcitation, and the voltage of the battery Cwillfall so slowly as to give the battery time to reduce its own voltagebefore the operation of the switch F, thus avoiding a flickering of thelights. By providing for a closin of switch 28 prior to shifting ofswitch ti, an interruption of the exciting current and consequentinjurious sparking at the point of interruption is avoided.

Since both batteries have to supply the lighting current connected inparallel when the train is stationary, both batteries must naturally becharged; this is effected by interchanging the connections of the, two

batteries atsuitable intervals, as for instance after every stoppage ofthe train, in the manner illustrated in my U. S. Patent No. 994,510above mentioned.

It is important that the connection of the two batteries C, Cestablished during the stoppage of the train, does not contain thecurrent coil H of the switch G, since otherwise the switch G might beoperated to its left-hand position by a compensating or equalizingcurrent flowing between the batteries.

Great advantages are effected bychanging the shunt excitation of thedynamo (switch G to the right) to regulation for constant voltage(switch G to the left), not before the dynamo has taken the entire loadof the work circuit. In this manner, the belt reaches the limit of itscapacity for transmitting power, before the dynamo has assumed theentire load, 2'. 0., while the dynamo is still running with shuntexcitation; upon further increase of speed, the

belt begins to slip in a perfectly stable manner, since when the beltslips the speed of the dynamo falls, and with shunt excitation thedynamo output will fall more rapidly than the speed, so that the dynamowill thereafter deliver just an amount of currentcorresponding to thepower-transmitting capacity of the belt.

In the other case. 6., if the shunt excitation will be replaced byregulation for constant voltage before the dynamo has assumed the entireload, and if the belt is not capable of transmitting the entire load,then the slipping of the belt will be unstable. The more the speed ofthe dynamo falls, in consequence of belt-slipping, the more theretarding force of the dynamo increases, owing to the constancy of thepower (constant volts X constant amp'eres) delivered by the dynamo.After a sufiicient decrease of the speed, the dynamo will be switchedout again, i. (5., completely discharged of load. Afterward a new riseof speed will take place until the dynamo is switched in again and soforth. In this manner there may take place an oscillating switching-inand switching-out of the controlling apparatus.

lly disconnecting the dynamo from the external circuit only after thedynamo output has been reduced practically to zero, the belt is neverslipping at the time the dynamo is disconnected, and no repeatedoperation of the cut-out switches occurs.

If the work circuit were connected to the terminals 39, 7 during theshunt excitation period, (switch F to the left, switch G to the right,and switch E deenergized), then with falling dynamo voltage the workcircuit voltage would drop to its permissible minimum of about 32 volts(and should be disconnected) sooner than the voltage at the chargingbattery C drops to its permissible minimum of two volts per cell (32volts), since the battery is across the high "oltage mains 46, 7 thiswould'require two switches, for load and battery respectively, operatingat different times. According to the present invention however, the workcircuit is connected to the high voltage terminals 46, 7, through theseries resistance R during the shunt excitation period, so that withfalling dynamo voltage the work circuit voltage reaches its lower limitof 32 volts at the same time that the battery voltage reaches its lowerlimit of 32 volts, so that both the work circuit and the battery may bedisconnected by a single switch mechanism as indicated at F. 9, 27. Bythis means it is possible to dispense with one of the prior artswitches, and thus in spite of simultaneous connection of the chargingcircuit and work circuit to the dynamo, to effect a gradual transfer ofthe load to the dynamo during the starting vehicles, such as motorveassumed first, that the train is at rest. At

this time switch F is in its right-hand position, switch Gr is at theright, and switch 15 is de'nergized; hence both batteries C and C areconnected in parallel to supply the work circuit D. If now the trainstarts, the

dynamo field B is self-excited by virtue of its connection to the mains39, 46 of the generator, through the ballast resistance R switch blade28 and leads 6, 29; the batteries C and. C are still in parallel withthe load. When the train speed is high enough so that current flows inthe direction from the main 46 through the voltage coil H to thepositive terminal of battery C switch F is shifted automatically to theleft: this does not disturb the connections frombattery C to loadthrough coil H and switch blade 10, but it disconnects battery C fromthe load, and connects this battery to the high-voltage or charging main46 of the generator through the current coil H and the ballast chargingresistance R Simultaneously the high-voltage main 46 of the generatorbecomes connected to the load in parallel with the batte C through theload or lamp resistance switch blade 27, lead 31, and switch blade thegenerator is still selfexcited through the circuit 46, R 28, 6, B, 39.When the train speed is high enough so that current flows from the main46 through the lamp resistance R switch blade 27, lead 31, switch blade30, switch blade 10, and current coil H into the positive terminal ofbattery C the olarity of the coil H4 is reversed and switch ,is shiftedautomatically to the left. The battery C is now still on charge throu hthe ballast resistance R, current coil the ballast field resistance,yvinding B, so that with variations of dynamo and switch blade 9; thethe high voltage main 46 of the generator and the battery C and loadD isbroken at the switch blade 30, and instead, the low voltage orintermediate main 39 of the generator is connected to the load D throughconnection between switch blade 30,- without any intermediate.

lamp resistance; the battery C? is now connected, throu h the currentcoil H, switch blade 10 and ead 6, to the jllzmction between and thefield spee a varia e amount. of. the s ant any but may be adapted,

ships and the like, and also in sta rent flowing through resistance Rverted from the field B into the battery C and thus constant voltage ismaintained at the generator irrespective of the generator speed, ashereinbefore explained. After a length of time depending upon thecondition of the slowly charging battery C the voltage of this batteryreaches the point where the voltage coil 8 (whose strength isproportional to the voltage of battery C becomes sufiiciently energizedto lift its switch blade is operation disconnects the field winding Bfrom the resistance R and hi hvoltage main 46, and as a result the fieldis now excited by discharge current pass' from the battery C through thecoil H, switch blade 10, main 6, and field winding B, to theintermediate or low-voltage main 39 of the generator, and, ashereinbefore explained, the exciting current is automatically decreasedwith any speed increase and the dynamo voltage thus maintained constantirrespective of the dynamo speed. If the dynamo speed drops below itsoperative value at a time when the batte C is thus discharging throughthe field B to the main 39 (switch E energized), the field currentpassing through the .coil H naturally increases with decreasing dynamospeed and when said current attains a predetermined maximum, such as forexample, ten amperes, the switch G is automatically shifted to theright.The voltage coil H is at this time energized and opposes the fluxgenerated by current coil H to such an extentthat ten amperes of currentthrough coil H is re uired to shift the switch G toward the rig t;thisshifting of the switch G toward the right interrupts for a moment atthe contacts 26 the circuit of voltage coil 8 of switch E, which is thuscompelled to retract its blade 28 and reestablish the selfexciting fieldcircuit 46, R 28, 6, B, 39. In

this manner, the'field circuit B is notopened and the objectionable,spar g attendant upon the opening of a field circuit is avoided.

Upon further decrease of d amo speed, the switch F shifts to the rightwhen reverse current from battery G nto main 46 reverses the eflect ofthe current coil H and the conditions existing with the train at rest(switches F and G ener ized) are thus restored. If, however, the dynamospeed drops below its minimum operative value at a time when the batte Cis connected to the junction between field resistance R and fieldwinding B (switch E denergized) the field current, part of which (forexample, eight amperes) is sufi plied by the constant current resistance3 and the rest of which is supplied b the battery C, naturally increaseswith ecreasing dynamo speed, and when said field current. attains apredetermined maximum, such as ten -P b We emr is to the right, switch Ede-' ing through the coil H from thebattery C the switch G isautomatically shifted to the right. The-voltage coil H is at this timede energized, and therefore offers no opposition to the coil H, so thattwo amperes of discharge current flowing through the coil H from thebattery C is sufficient to shift the switch G toward the right. Uponfurther decrease in train speed, the reverse current, from battery 'Cinto the main -16 reverses the current coil H and shifts the switch F tothe right. The conditions corresponding to yero train speed, are thusrestored, namely, switches F and G to the right, and switch Edeenergized, with the two batteries in parallel serving the load.

From the above it will be seen that the several objects of the inventionare realized and other advantageous results obtained.

As various changes might be made in the above construction, and as theabove invention might be embodied in diiferent forms, it is intendedthat all matter set forth in the above description and in theaccompanying drawings, shall be interpreted as illustrative and not in alimiting What I claim is 1. In apparatus of the class described, incombination, a generator, a field coil therefor, a .suhstantiallyconstant current resistance connecting one end of said coil to one ofthe terminals of said generator, a battery connecting said same end toanother terminal of said generator, and protective means fordisconnecting said battery when a maximum field current is reached.

2. In apparatus of the class described, in combination, a generator,self-exciting and externalexciting means therefor, adapted to operateseparately or conjointly, and a de vice controlling said external means,to limit the maximum total' excitation of said generator toapredetermined value whether said external means is operating solely orconjointly with said self-exciting means.

3. In apparatus of the class described, in combination, a generatorhaving two commutators in series, providing thereby a positive,intermediate and negative terminal, an exciting winding, one pole ofwhich is connected to said intermediate terminal, a battery, one pole ofwhich is connected to said negative terminal, means for connecting anddisconnecting the other pole of the exciting winding and the other poleof the battery, and means for disconnecting the exclting from thebattery when the exciting current has attained a redetermined value.

4. In apparatus of e class described, in combination, a generator havingtwo commutators in series, providing thereby a posisense.

tive, intermediate and negative terminal, an

exciting winding, one pole of which is connected to said intermediateterminal, a battery, one pole of which is QQmlQQted to said ed to saidintermediate terminal and negative terminal, and means for connectingthe other pole of the exciting winding to the other pole of the batteryautomatically when the generator has assumed the load, said connectionfrom exciting winding to battery being automatically broken upon asufiicient decrease of generator speed.

5. In apparatus of the class described, in combination, a generatorhaving a positive terminal, a'negative terminal, and a terminal ofvoltage intermediate the voltage of the positive and negative terminals,an exciting winding for the generator connected to the intermediateterminal and the positive terminal through a constant-currentresistance, means for interrupting the connection between said windingand said positive terminal when the generator voltage has attained apredetermined value, and a battery whose poles are connectedrespectively to the negative terminal of the generator and to thepositive terminal of the exciting winding.

6. In apparatus of the class described, in combination, a generator, anexciting winding therefor connected to said generator through aconstant-current resistance, a hattery connected to said excitingwinding and to said generator so that the battery voltage and thegenerator voltage are opposed to each other, and means for interruptingthe connection between said winding and a terminal of said generatorwhen the battery voltage has attained a predetermined value,

7. In apparatus of the class described, in combination, a generatorhaving a positive terminal, a negative terminal, and a terminal ofvoltage intermediate the voltage of the positive and negative terminals,an exciting winding for the generator connected to the intermediateterminal and the positive terminal through a constant-currentresistance, whereby the current through said resistance normally dividesbetween exciting winding and battery to maintain the generator voltageconstant with varying speed, and means for interrupting the connectionbetween said winding and said positive terminal, whereupon the currentin said winding is proportional to the difference between batteryvoltage and the voltage across the intermediate and negative terminalsof the generator, whereby the generator voltage is maintained constantwith varying speed.

8. In apparatus of the classdescribed, i1 combination, a generatorhaving two com mutators in series, providing thereby a posi tive,intermediate and negative terminal, an exciting winding for thegenerator connect to battery whose other le is connected to th negativeterminal oi the generator, a con nection between the positive terminalof th generator and the junction between excit mg winding and battery,voltage-controlle means for breaking said connection, and means forrestoring said connection automatically prior to disconnection of thebattery from the exciting winding.

9. In apparatus of the class described, in combination, a generator, afield winding therefor, a battery adapted to be automatically connectedto the generator for charging thereby, means for simultaneouslyconnecting the generator to a work circuit through a resistance, meansautomatically effective after the generator has assumed the load, forbreaking said connection to the work circuit and connecting said workcircuit to generator terminals carrying only a fraction of the totalgenerator voltage, and means for re-connecting the work circuit to thegenerator-through said resistance prior to disconnection of thegenerator entirely from the work circuit.

10. In apparatus of the class described, in combination, a generatorhaving three terminals, namel a negative terminal, an intermediateterminal and a positive terminal, the voltage between negative terminaland positive terminal being higher than the voltage between negativeterminal and intermediate terminal, an exciting winding, one pole ofwhich is connected with said intermediate terminal and the other polewith said positive terminal, a resistance in the connection between saidpositive terminal and said exciting winding, a magnetic interrupteradapted to break said connection between positive terminal and excitingwinding, said interrupter having a voltage coil across the negativeterminal and the intermediate terminal, a battery whose negative pole isconnected to said negative terminal of the generator, a work circuitwhose negative pole is connected to said negative terminal of thegenerator, an auxiliary con necting line, a magnetic switch connectingin its working position the positive pole of said battery with thesecond pole of said exciting winding and connecting the positive pole ofthe work circuit with the intermediate terminal of the generator, saidswitch connecting in its rest position the positive pole of the batterywith the positive pole of the work circuit and connecting the latterwith said auxiliary connecting line, said switch shifting to its workingposition when current flows into said battery,

circuit which is closed when said interrupter has interrupted saidconnecting line, said second coil opposing said first coil; a secondbattery whose negative pole is connected to the negative pole of thegenerator, a second switch connecting in its working position thepositive pole of the second battery with the positive terminal of thegenerator and connecting said auxiliary connecting line with thepositive pole of the generator, said second switch connecting in itsrest position the positive pole of the second battery with the positivepole of the first battery, means for shifting said second switch intoits working position when the voltage of the positive terminal of thegenerator exceeds the voltage of the positive pole of the secondbattery, means for shifting said second switch into its rest positionwhen reverse current flows from said second battery to said generator, aresistance in the connecting line between the positive pole of thegenerator and said second switch, and a resistance in said auxiliaryconnecting line.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

HUGO GROB.

Witnesses HERMANN HUBER, CARL Goran.

